Overall efficiency optimization for power flow in dual-mode electro-mechanical variable transmission system

An overall efficiency definition is proposed with considerations of the power losses in engine, several electric motors, power coupling mechanism and battery pack. The efficiency models for planetary coupling mechanism, engine, motors and battery pack are built respectively, based on which an overall power flow efficiency model for a dual-mode electro-mechanical variable transmission system is established with enhancing energy transfer efficiency as objective, and an optimization is conducted. Then the optimized results are input to a comprehensive controller for hardware-in-the-loop simulation. The results of simulation show that the method of overall power flow efficiency optimization can optimally coordinate the working points of engine and several motors according to overall efficiency, and compared with traditional power-flow optimization method based solely on engine optimal working region, it further enhances the fuel economy and transmission efficiency of system. The research provides a theoretical basis for the development of overall control strategy and control system.